Clinical update on the pharmacology, efficacy and safety of transdermal buprenorphine

Assessment of the potential of novel and classical opioids to induce respiratory depression in mice

BACKGROUND AND PURPOSE

Opioid-induced respiratory depression limits the use of μ-opioid receptor agonists in clinical settings and is the main cause of opioid overdose fatalities. The relative potential of different opioid agonists to induce respiratory depression at doses exceeding those producing analgesia is understudied despite its relevance to assessments of opioid safety. Here we evaluated the respiratory depressant and anti-nociceptive effects of three novel opioids and relate these measurements to their in vitro efficacy.

EXPERIMENTAL APPROACH

Respiration was measured in awake, freely moving male CD-1 mice using whole body plethysmography. Anti-nociception was measured using the hot plate test. Morphine, oliceridine and tianeptine were administered intraperitoneally, whereas methadone, oxycodone and SR-17018 were administered orally. Receptor activation and arrestin-3 recruitment were measured in HEK293 cells using BRET assays.

KEY RESULTS

Across the dose ranges examined, all opioids studied depressed respiration in a dose-dependent manner, with similar effects at the highest doses, and with tianeptine and oliceridine showing reduced duration of effect, when compared with morphine, oxycodone, methadone and SR-17018. When administered at doses that induced similar respiratory depression, all opioids induced similar anti-nociception, with tianeptine and oliceridine again showing reduced duration of effect. These data were consistent with the in vitro agonist activity of the tested compounds.

CONCLUSION AND IMPLICATIONS

In addition to providing effective anti-nociception, the novel opioids, oliceridine, tianeptine and SR-17018 depress respiration in male mice. However, the different potencies and kinetics of effect between these novel opioids may be relevant to their therapeutic application in different clinical settings.

An Examination of the Complex Pharmacological Properties of the Non-Selective Opioid Modulator Buprenorphine

The goal of this review is to provide a recent examination of the pharmacodynamics as well as pharmacokinetics, misuse potential, toxicology, and prenatal consequences of buprenorphine. Buprenorphine is currently a Schedule III opioid in the US used for opioid-use disorder (OUD) and as an analgesic. Buprenorphine has high affinity for the mu-opioid receptor (MOR), delta (DOR), and kappa (KOR) and intermediate affinity for the nociceptin (NOR). Buprenorphine's active metabolite, norbuprenorphine, crosses the blood-brain barrier, is a potent metabolite that attenuates the analgesic effects of buprenorphine due to binding to NOR, and is responsible for the respiratory depressant effects. The area under the concentration curves are very similar for buprenorphine and norbuprenorphine, which indicates that it is important to consider this metabolite. Crowding sourcing has identified a buprenorphine street value (USD 3.95/mg), indicating some non-medical use. There have also been eleven-thousand reports involving buprenorphine and minors (age < 19) at US poison control centers. Prenatal exposure to clinically relevant dosages in rats produces reductions in myelin and increases in depression-like behavior. In conclusion, the pharmacology of this OUD pharmacotherapy including the consequences of prenatal buprenorphine exposure in humans and experimental animals should continue to be carefully evaluated.

Cancer Pain Management: A Narrative Review of Current Concepts, Strategies, and Techniques

Pain is frequently reported during cancer disease, and it still remains poorly controlled in 40% of patients. Recent developments in oncology have helped to better control pain. Targeted treatments may cure cancer disease and significantly increase survival. Therefore, a novel population of patients (cancer survivors) has emerged, also enduring chronic pain (27.6% moderate to severe pain). The present review discusses the different options currently available to manage pain in (former) cancer patients in light of progress made in the last decade. Major progress in the field includes the recent development of a chronic cancer pain taxonomy now included in the International Classification of Diseases (ICD-11) and the update of the WHO analgesic ladder. Until recently, cancer pain management has mostly relied on pharmacotherapy, with opioids being considered as the mainstay. The opioids crisis has prompted the reassessment of opioids use in cancer patients and survivors. This review focuses on the current utilization of opioids, the neuropathic pain component often neglected, and the techniques and non-pharmacological strategies available which help to personalize patient treatment. Cancer pain management is now closer to the management of chronic non-cancer pain, i.e., "an integrative and supportive pain care" aiming to improve patient's quality of life.

Effectiveness of two extended-release buprenorphine formulations during postoperative period in neonatal rats

Information on the effectiveness of a new long-lasting buprenorphine formulation, extended-release buprenorphine, in the neonatal rat is very limited. This study compares whether a high dose of extended-release buprenorphine (XR-Hi) attenuates thermal hypersensitivity for a longer period than a low dose of extended-release buprenorphine (XR-Lo) in a neonatal rat incisional pain model. Two experiments were performed. Experiment one: Male and female postnatal day-5 rat pups (n = 38) were randomly assigned to 1 of 4 treatment groups and received a subcutaneous administration of one of the following: 1) 0.9%NaCl (Saline), 0.1 mL; 2) sustained release buprenorphine (Bup-SR), 1 mg/kg; 3) XR-Lo, 0.65 mg/kg; and 4) XR-Hi, 1.3 mg/kg. Pups were anesthetized with sevoflurane in 100% O₂ and a 5 mm long skin incision was made over the left lateral thigh and underlying muscle dissected. The skin was closed with surgical tissue glue. Thermal hypersensitivity testing (using a laser diode) and clinical observations were conducted 1 hour (h) prior to surgery and subsequently after 1, 4, 8, 24, 48, 72 h of treatment. Experiment two: The plasma buprenorphine concentration level was evaluated at 1, 4, 8, 24, 48, 72 h on five-day-old rat pups. Plasma buprenorphine concentration for all treatment groups remained above the clinically effective concentration of 1 ng/mL for at least 4 h in the Bup-SR group, 8 h in XR-Lo and 24 h in XR-Hi group with no abnormal clinical observations. This study demonstrates that XR-Hi did not attenuate postoperative thermal hypersensitivity for a longer period than XR-Lo in 5-day-old rats; XR-Hi attenuated postoperative thermal hypersensitivity for up to 4 h while Bup-SR and XR-Lo for at least 8 h in this model.

Triglyceride-Mimetic Prodrugs of Buprenorphine Enhance Oral Bioavailability via Promotion of Lymphatic Transport

Buprenorphine (BUP) is a potent opioid analgesic that is widely used for severe pain management and opioid replacement therapy. The oral bioavailability of BUP, however, is significantly limited by first-pass metabolism. Previous studies have shown that triglyceride (TG) mimetic prodrugs of the steroid hormone testosterone circumvent first-pass metabolism by directing drug transport through the intestinal lymphatics, bypassing the liver. The current study expanded this prodrug strategy to BUP. Here different self-immolative (SI) linkers were evaluated to conjugate BUP to the 2 position of the TG backbone via the phenol group on BUP. The SI linkers were designed to promote drug release in plasma. Lipolysis of the prodrug in the intestinal tract was examined via incubation with simulated intestinal fluid (SIF), and potential for parent drug liberation in the systemic circulation was evaluated via incubation in rat plasma. Lymphatic transport and bioavailability studies were subsequently conducted in mesenteric lymph duct or carotid artery-cannulated rats, respectively. TG prodrug derivatives were efficiently transported into the lymphatics (up to 45% of the dose in anaesthetised rats, vs. less than 0.1% for BUP). Incorporation of the SI linkers facilitated BUP release from the prodrugs in the plasma and in concert with high lymphatic transport led to a marked enhancement in oral bioavailability (up to 22-fold) compared to BUP alone. These data suggest the potential to develop an orally bioavailable BUP product which may have advantages with respect to patient preference when compared to current sublingual, transdermal patch or parenteral formulations.

Complete opioid transition to sublingual Buprenorphine after abdominal surgery is associated with significant reductions in opioid requirements, but not reduction in hospital length of stay: a retrospective cohort study

Background

The use of sublingual buprenorphine (SLBup) for acute pain after major abdominal surgery may offer the potential advantages of unique analgesic properties and more reliable absorption during resolving ileus. We hypothesized that complete opioid transition to SLBup rather than oral oxycodone (OOxy) in the early postoperative period after major abdominal surgery would reduce hospital length of stay, and acute pain and total OMEDD (Oral Morphine Equivalent Daily Dose) requirements in the first 24 h from post-parenteral opioid transition.

Methods

We reviewed 146 patients who had undergone elective and emergency abdominal surgery under our quaternary referral centre’s Upper Gastro-Intestinal and Colo-Rectal Surgical Units 6 months before and after the introduction of complete postoperative transition to sublingual buprenorphine, rather than oral oxycodone, in July 2017. Our primary endpoint was 24-hourly post-transition OMEDDs; secondary endpoints were 24-hourly post-transition Mean NRS-11 pain scores on movement (POM) and length of hospital stay (LOS). Univariate analysis and linear multivariate regression analyses were used to quantify effect size and identify surgical, patient & other analgesic factors associated with these outcome measures.

Results

Patients transitioning to SLBup had reduced 24-hourly post-transition OMEDD requirements on postoperative day 2 (POD) (26 mg less, p = 0.04) and NRS-11 POM at POD1 (0.7 NRS-11 units less, p = 0.01). When adjusting for patient, surgical and special analgesic factors, SLBup was associated with a similar reduction in OMEDDs (Unstandardised beta-coefficient -26 mg, p = 0.0001), but not NRS-11 POM (p = 0.47) or hospital LOS (p = 0.16).

Conclusions

Our change of practice from use of OOxy to SLBup as primary transition opioid from patient-controlled analgesia delivered full opioid agonists was associated with a clinically significant decrease in 24-hourly post-parenteral opioid transition OMEDDs and improved NRS-11 POM, but without an association with hospital LOS after major abdominal surgery. Further prospective randomized work is required to confirm these observed associations and impact on other important patient-centred outcomes.

Evaluation of Buprenorphine Rotation in Patients Receiving Long-term Opioids for Chronic Pain: A Systematic Review

IMPORTANCE

Individuals with chronic pain who use long-term opioid therapy (LTOT) are at risk of opioid use disorder and other harmful outcomes. Rotation to buprenorphine may be considered, but the outcomes of such rotation in this population have not been systematically reviewed.

OBJECTIVE

To synthesize the evidence on rotation to buprenorphine from full μ-opioid receptor agonists among individuals with chronic pain who were receiving LTOT, including the outcomes of precipitated opioid withdrawal, pain intensity, pain interference, treatment success, adverse events or adverse effects, mental health condition, and health care use.

EVIDENCE REVIEW

PubMed, CINAHL, Embase, and PsycInfo were searched from inception through November 3, 2020, for peer-reviewed original English-language research that reported the prespecified outcomes of rotation from prescribed long-term opioids to buprenorphine among individuals with chronic pain. Two independent reviewers extracted data as well as assessed risk of bias and study quality according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines. Quality of evidence was assessed with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system.

FINDINGS

A total of 22 studies were analyzed, of which 5 (22.7%) were randomized clinical trials, 7 (31.8%) were case-control or cohort studies, and 10 (45.5%) were uncontrolled pre-post studies, which involved 1616 unique participants (675 female [41.8%] and 941 male [58.2%] individuals). Six of the 22 studies (27.3%) were primary or secondary analyses of a large randomized clinical trial. Participants had diverse pain and opioid use histories. Rationale for buprenorphine rotation included inadequate analgesia, intolerable adverse effects, risky opioid regimens (eg, high dose and/or sedative coprescriptions), and aberrant opioid use. Most protocols were adapted from protocols for initiating treatment in patients with opioid use disorder and used buccal or sublingual buprenorphine. Very low-quality evidence suggested that buprenorphine rotation was associated with maintained or improved analgesia, with a low risk of precipitating opioid withdrawal. Steady-dose buprenorphine was better tolerated than tapered-dose buprenorphine. Adverse effects were manageable, and severe adverse events were rare. Only 2 studies evaluated mental health outcomes, but none evaluated health care use. Limitations included a high risk of bias in most studies.

CONCLUSIONS AND RELEVANCE

In this systematic review, buprenorphine was associated with reduced chronic pain intensity without precipitating opioid withdrawal in individuals with chronic pain who were receiving LTOT. Future studies are necessary to ascertain the ideal starting dose, formulation, and administration frequency of buprenorphine as well as the best approach to buprenorphine rotation.

Transdermal Buprenorphine Use for Pain Management in Palliative Care

Cancer related pain is prevalent among patients with a cancer diagnosis, occurring from the tumor itself or as a result of treatment. Many patients require opioid therapy to manage pain and providers must balance efficacy with side effects. Transdermal buprenorphine (TDB) has shown promise for pain management, however, the maximum dose available in the US is considered low, resulting in doubts of efficacy. This study set out to assess if the patch strengths available in the US (5-20 mcg/hour) are able to provide analgesia for patients with cancer in a palliative medicine clinic. This retrospective chart review analyzed patient charts for outpatient TDB use within a palliative medicine clinic in the United States. Patients had to have a follow up visit with the clinic in order to be included. Sixty-eight patients were included for analysis with 54 (79%) continuing at least 28 days and 37 (54%) continuing for at least 84 days. The median change in pain score was 0, though 25 (46%) of patients reported a decrease of 1 or more points at the first follow up. TDB is a viable option for cancer related pain for select patients, demonstrated by duration of use and stable reporting of pain.

Design and Synthesis In Silico Drug-like Prediction and Pharmacological Evaluation of Cyclopolymethylenic Homologous of LASSBio-1514

Acylhydrazones are still an important framework to the design of new bioactive compounds. As treatment of chronic pain represents a clinical challenge, we decided to modify the structure of LASSBio-1514 (1), previously described as anti-inflammatory and analgesic prototype. Applying the homologation as a strategy for molecular modification, we designed a series of cyclopentyl- (2a-e), cyclobutyl- (3a-e), and cyclopropylacylhydrazones (4a-e) that were synthetized and evaluated in murine models of inflammation and pain. A comparison of their in silico physicochemical and drug-like profile was conducted, as well as their anti-inflammatory and analgesic effect. Compounds 4a (LASSBio-1755) and 4e (LASSBio-1757) displayed excellent in silico drug-like profiles and were identified as new analgesic lead-candidates in acute and chronic model of pain, through oral administration.

Oral and buccal abuse of transdermal opioids : an underdetected but potentially lethal practice

Objectives : Transdermal opioid patches (TOPs) are effective and well tolerated in patients with moderate to severe chronic pain syndromes. Their specific pharmacological properties, however, make them prone to abuse. The objective of this article is to describe the practice of oral and buccal abuse of TOPs and to discuss its clinical implications. Methods : We present the case of a patient admitted to the intensive care unit after oral abuse of transdermal opioid patches. Additionally, a narrative literature review on the topic is conducted, referring to Pubmed and Embase. Results : Oral or buccal TOP abuse is the most frequent method of TOP abuse, followed by intravenous injection, inhaling, and applying multiple patches. The main reasons for TOP abuse include drug addiction, suicidal behavior and self-medication. Oral ingestion is potentially lethal because of the high doses of fentanyl that are found in a single patch. Buccal abuse results in fast elevations of fentanyl serum concentrations, caused by transmucosal absorption of fentanyl, thus bypassing hepatic metabolism. During emergency management, naloxone should be administered in a continuous infusion, given the high risk of recurrence of symptoms. Evidence suggests that transdermal buprenorphine is safer in terms of abuse potential. This is explained by its ceiling effect for respiratory depression and its lower peak effects in supratherapeutic doses. Risk factors for abuse include history of substance use disorder, prior opioid overdose and mental illness. Patients with suspected opioid abuse should be referred to pain clinics, mental health specialists or drug addiction facilities. Conclusion : Oral or buccal abuse is the most reported non-dermal form of TOP abuse. When ingested or chewed, TOPs pose considerable health risks. It is critical to screen patients with chronic opioid therapy regularly for opioid use disorder. When confronted with patients at risk of abuse, close monitoring and referral to specialist care is advised.

Benefit-Risk Analysis of Buprenorphine for Pain Management

Health care providers in the United States are facing challenges in selecting appropriate medication for patients with acute and chronic pain in the midst of the current opioid crisis and COVID-19 pandemic. When compared with conventional opioids, the partial µ-opioid receptor agonist buprenorphine has unique pharmacologic properties that may be more desirable for pain management. The formulations of buprenorphine approved by the US Food and Drug Administration for pain management include intravenous injection, transdermal patch, and buccal film. A comparison of efficacy and safety data from studies of buprenorphine and conventional opioids suggests that buprenorphine may be a better-tolerated treatment option for many patients that provides similar or superior analgesia. Our benefit-risk assessment in this narrative review suggests that health care providers should consider that buprenorphine may be an appropriate alternative for pain management over other opioids.

The Pharmacology of Buprenorphine Microinduction for Opioid Use Disorder

Although expanding the availability of buprenorphine—a first-line pharmacotherapy for opioid-use disorder (OUD)—has increased the capacity of healthcare systems to offer treatment, starting this medication is fraught with significant barriers. Standard induction regimens require persons with OUD to taper and discontinue full opioid agonists and experience opioid withdrawal prior to the first dose of buprenorphine. Further, emerging evidence indicates that precipitated withdrawal during induction may impact long-term treatment outcomes. Microinduction is a novel approach that, by harnessing buprenorphine’s unique pharmacological profile, may allow circumventing the needed for prolonged opioid tapers, and reduce the risk of precipitated withdrawal—holding promise to enhance treatment access. In this review, we examine the pharmacological basis for microinduction and appraise the evidence of this approach to improve clinical outcomes among persons with OUD. First, we highlight the potential dose-dependent effects of buprenorphine on two key neuroadaptations at the mu-opioid receptor (MOR)—resensitization and upregulation. We then focus on how microinduction may reverse these chronic MOR neuroadaptations, allowing the maintenance of an adequate opioid tone, and thereby potentially circumventing opioid withdrawal. Second, we describe the clinical evidence available, derived from observational reports and open-label studies, examining the potential efficacy of microinduction. Despite significant heterogeneity—exemplified by variable buprenorphine formulations, daily doses, and schedules of administration—these data provide preliminary support for the feasibility of microinduction. Finally, we provide new mechanistic, methodological, and clinical insights to guide future translational research, as well as randomized, placebo-controlled clinical trials in this compelling agenda of pharmacotherapy development.

The Role of Opioids in Pain Management in Elderly Patients with Chronic Kidney Disease: A Review Article

Chronic kidney disease (CKD) is a global public health problem. Pain is one of the most generally experienced symptoms by CKD patients. Pain management is a key clinical activity; nonetheless, insufficient pain management by health professionals keeps it up. Opioids as pain relievers are a class of naturally-derived and synthetic medications. They act through interactions with receptors in peripheral nerves. Numerous pharmacokinetic alterations happen with aging that influence drug disposition, metabolism, and quality of life. Acetaminophen alone, or combined with low-potency opioid dose is regarded as the safest pain-relieving choice for CKD. Morphine and codeine are probably eluded in renal impairment patients and used with excessive carefulness. Tramadol, oxycodone, and hydromorphone can be used by patient monitoring, while methadone, transdermal fentanyl, and buprenorphine seem to be safe to use in older non-dialysis patients with renal impairment. Consistent with the available literature, the main aim of this review was to explore the occurrence of chronic pain and its opioid treatment in CKD patients. According to this review, more and well-made randomized controlled trials are necessary to find appropriate opioid doses and explore the occurrence of side effects.

Drug use evaluation of opioid analgesics in pain management among patients with hematopoietic stem cell transplantation

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) patients usually experience mucositis, musculoskeletal pain associated with high-dose chemotherapy, radiation, post-HSCT infection, or graft-versus-host disease. Pain management is important for the patients' quality of life. We evaluated appropriate opioid analgesic use in HSCT patients to propose effective pain management strategies.

METHODS

A retrospective analysis was conducted using electronic medical records of adult patients with HSCT treated with opioids for moderate to severe pain at Seoul National University Bundang Hospital. The numeric rating scale (NRS) was used in pain management. NRS scores of 4‒10 correspond to moderate to severe pain. Appropriate opioid analgesic use was evaluated following published cancer pain management guidelines.

RESULTS

In total, 119 cases were evaluated, including 369 episodes of moderate to severe pain. Mucositis-related, musculoskeletal, and headache pain occurred in 62.6%, 25.8%, and 6.0% of episodes, respectively. Frequently used opioids were intravenous tramadol (84.9%), fentanyl patch (73.9%), and intravenous morphine sulfate (68.9%). Intravenous and topical administrations were used for mucosal pain. In total, 95.0% of patients received appropriate short-acting opioids for initial pain management, 80.5% received appropriate doses of short-acting opioids, appropriate opioids dose adjustment was done after first assessment in 95.5% of patients, and 85.6% were converted to appropriate long-acting opioids.

CONCLUSION

Short-acting opioid analgesic use for initial pain management and dose adjustment after assessment were appropriate. However, initial and conversion dosages recommended by guidelines may be difficult to implement considering the severity of HSCT patients. Pain management guidelines specific for HSCT patients should be developed in the future.

Safe Use of Opioids in Chronic Kidney Disease and Hemodialysis Patients: Tips and Tricks for Non-Pain Specialists

In patients suffering from moderate-to-severe chronic kidney disease (CKD) or end-stage renal disease (ESRD), subjected to hemodialysis (HD), pain is very common, but often underestimated. Opioids are still the mainstay of severe chronic pain management; however, their prescription in CKD and HD patients is still significantly low and pain is often under-treated. Altered pharmacokinetics and the lack of clinical trials on the use of opioids in patients with renal impairment increase physicians' concerns in this specific population. This narrative review focused on the correct and safe use of opioids in patients with CKD and HD. Morphine and codeine are not recommended, because the accumulation of their metabolites may cause neurotoxic symptoms. Oxycodone and hydromorphone can be safely used, but adequate dosage adjustments are required in CKD. In dialyzed patients, these opioids should be considered as second-line agents and patients should be carefully monitored. According to different studies, buprenorphine and fentanyl could be considered first-line opioids in the management of pain in CKD; however, fentanyl is not appropriate in patients undergoing HD. Tapentadol does not need dosage adjustment in mild-to-moderate renal impairment conditions; however, no data are available on its use in ESRD. Opioid-related side effects may be exacerbated by common comorbidities in CKD patients. Opioid-induced constipation can be managed with peripherally-acting-μ-opioid-receptor-antagonists (PAMORA). Unlike the other PAMORA, naldemedine does not require any dose adjustment in CKD and HD patients. Accurate pain diagnosis, opioid titration and tailoring are mandatory to minimize the risks and to improve the outcome of the analgesic therapy.

An analysis of the safety and efficacy of dexmedetomidine in posterior spinal fusion surgery for adolescent idiopathic scoliosis: a prospective randomized study

PURPOSE

To evaluate whether use of dexmedetomidine, a centrally acting α2 adrenergic agonist, reduces opioid consumption in PSF.

METHODS

Adolescent idiopathic scoliosis patients who underwent PSF were randomized into morphine (M) and dexmedetomidine (D) group. M group received a 10 μg/kg/h IV infusion of morphine for 24 h post-surgery, while the D group received a 0.4 μg/kg/h IV infusion of dexmedetomidine. Trained nursing staffs recorded hourly vital parameters (blood pressure, pulse rate, respiratory rate, and oxygen saturation). Pain, postoperative nausea/vomiting (PONV), and sedation were rated using: the numerical rating scale (NRS), the PONV scale, and sedation status scale (SS). Preemptive analgesia with gabapentin and postoperative analgesia with ketorolac and paracetamol were used in both the groups. Any complications in the study groups were recorded.

RESULTS

No significant difference was noted between the groups (M vs D) with respect to NRS (3.1 ± 0.8 vs 2.7 ± 0.5) (p = 0.07) and breakthrough analgesia requirements (0.78 vs 0.45) (p = 0.17). A significant difference was noted between the groups with respect to the secondary outcome measures of time to ambulation (56.6 ± 12.7 h vs 45.2 ± 7.7 h), time to oral analgesics (84.3 ± 20 h vs 64.0 ± 15.4 h), and time to liquid intake (8.3 ± 1.3 h vs 7.2 ± 1.2 h). The M group had a higher PONV score (0.46 ± 0.3 vs 0.16 ± 0.1) (p < 0.001) and mean time to bowel opening (112.7 ± 28.4 h vs 90.1 ± 20.5 h) (p < 0.001). Additionally, the enema or suppository requirements for bowel opening were significantly more (0.59 ± 0.6 vs 0.26 ± 0.4) (p = 0.01) in the M group.

CONCLUSION

Dexmedetomidine provided analgesia comparable to morphine with lower PONV scores. It also reduced the opioid requirements in the PSF patients without additional complications and can therefore be incorporated in pain management protocols.

[Transdermal buprenorphine for acute postoperative pain: a systematic review]

BACKGROUND AND OBJECTIVES

Postoperative pain is still a major concern in several surgical procedures. Multimodal analgesia is best for postoperative pain management; however, opioid therapy is still the main treatment for pain after surgical procedures. Transdermal buprenorphine is a partial μ agonist opioid widely used for chronic pain syndromes, with limited evidence for acute postoperative pain. A systematic review of studies examining transdermal buprenorphine for acute pain management after surgery was conducted.

CONTENTS

Data from PubMed, Embase, The Cochrane Central Register of Controlled Trials (CENTRAL), CINAHL via EBSCOhost, and LILACS were reviewed, including randomized clinical trials that evaluated total postoperative pain, postoperative analgesic consumption, drug-related side effects and patient satisfaction with analgesia regimen. Data from nine studies (615 patients) were included in this review. Most studies initiated transdermal buprenorphine use 6 to 48 hours before surgery, maintaining use from 1 to 8 days after the procedure. Most studies showed lower or similar postoperative pain scores, postoperative analgesic consumption and patient satisfaction comparing buprenorphine to placebo, tramadol, celecoxib, flurbiprofen and parecoxib. The incidence of side effects varied between studies, with most showing no increase in drug-related side effects with buprenorphine use, except one study, which compared buprenorphine to oral tramadol, and one to transdermal fentanyl. However, most results were derived from evidence with an overall high or unclear risk of bias.

CONCLUSIONS

Although more studies are necessary, initial results show that transdermal buprenorphine seems to be an effective and safe opioid choice for management of acute postoperative pain.

Adjuvants in pain medicine. Selection of the drug depending on the desired effect – so which drug to choose?

To date, much research has focused on finding the ideal adjuvant for local anesthetics. Each of them can have different effects. In anesthesiology and pain medicine, depending on the purpose, one or another effect may be desirable. For example, in some situations it is desirable to accelerate the onset of action or prolong the duration of the block, in others the desired effect may be a “response to intravascular administration”, it should also be borne in mind that not all adjuvants are allowed for intrathecal administration.

Physiologically-Based Pharmacokinetic (PBPK) Modeling of Buprenorphine in Adults, Children and Preterm Neonates

Buprenorphine plays a crucial role in the therapeutic management of pain in adults, adolescents and pediatric subpopulations. However, only few pharmacokinetic studies of buprenorphine in children, particularly neonates, are available as conducting clinical trials in this population is especially challenging. Physiologically-based pharmacokinetic (PBPK) modeling allows the prediction of drug exposure in pediatrics based on age-related physiological differences. The aim of this study was to predict the pharmacokinetics of buprenorphine in pediatrics with PBPK modeling. Moreover, the drug-drug interaction (DDI) potential of buprenorphine with CYP3A4 and P-glycoprotein perpetrator drugs should be elucidated. A PBPK model of buprenorphine and norbuprenorphine in adults has been developed and scaled to children and preterm neonates, accounting for age-related changes. One-hundred-percent of the predicted AUC_last values in adults (geometric mean fold error (GMFE): 1.22), 90% of individual AUC_last predictions in children (GMFE: 1.54) and 75% in preterm neonates (GMFE: 1.57) met the 2-fold acceptance criterion. Moreover, the adult model was used to simulate DDI scenarios with clarithromycin, itraconazole and rifampicin. We demonstrate the applicability of scaling adult PBPK models to pediatrics for the prediction of individual plasma profiles. The novel PBPK models could be helpful to further investigate buprenorphine pharmacokinetics in various populations, particularly pediatric subgroups.

Analgesic impact of buprenorphine transdermal patch in total hip arthroplasty: A randomized controlled trial protocol

BACKGROUND

The efficacy and safety of buprenorphine transdermal patch (BTP) has been well established in chronic pain, but data regarding acute postoperative pain relief is still very limited. Therefore, we design a prospective, randomized, controlled study to evaluate the effectiveness and safety of the BTP for postoperative analgesia in total hip arthroplasty.

METHODS

This study is designed as a single-center, prospective, double-blind, randomized controlled trial. Group A receives a 10 mg patch of buprenorphine at the conclusion of surgery which is continued for 14 days. Group B receives a conventional analgesic regimen, that is, IV paracetamol 1 mg every 8 hours alternating with parenteral tramadol 50 mg every 8 hours for the first 2 postoperative days followed by oral administration of the same drug still the end of 2 weeks. A total of 160 patients are needed with an allowance for 10% drop-out. The primary outcome of this noninferiority study is opioid consumption within the first 24 hours following surgery. The secondary outcomes included numerical rating scale scores at rest, postoperative complications, length of hospital stay, and patient satisfaction.

RESULTS

This trial is expected to be the largest randomized trial assessing the efficacy of BTP after primary total hip arthroplasty and powered to detect a potential difference in the primary outcome.

TRIAL REGISTRATION NUMBER

This study protocol was registered in Research Registry (researchregistry5524).

Evidence for Continuing Buprenorphine in the Perioperative Period

OBJECTIVE

Given there are conflicting recommendations for the perioperative management of buprenorphine, we conducted a retrospective cohort study of our surgery patients on buprenorphine whose baseline dose had been preoperatively continued, tapered, or discontinued.

MATERIALS AND METHODS

We reviewed charts of patients on buprenorphine who had received elective surgery at Stanford Healthcare from January 1, 2013 to June 30, 2016. Our primary outcome of interest was the change in pain score, defined as mean postoperative pain score-preoperative pain score. We also collected data on patients' tapering procedure and any postoperative nonbuprenorphine opioid requirements.

RESULTS

Out of ∼1200 patients on buprenorphine, 121 had surgery of which 50 were admitted and included in the study. Perioperative continuation of transdermal buprenorphine resulted in a significantly lower change in pain score postoperatively (0.606±0.878) than discontinuation (4.83±1.23, P=0.012). Among sublingual patients, there was no statistically significant difference in the change in pain score between those who were tapered to a nonzero dose versus discontinued (P=0.55). Continuation of sublingual buprenorphine resulted in fewer nonbuprenorphine scheduled opioid prescriptions than its taper or discontinuation (P=0.028). Finally, tapers were performed with great variability in the tapering team and rate of taper.

DISCUSSION

On the basis of our findings, we implemented a policy at our institution for the continuation of perioperative buprenorphine whenever possible. Our work reveals crucial targets for the education of perioperative healthcare providers and the importance of coordination among all perioperative services and providers.

New Medications for Neuropsychiatric Disorders

This article seeks to summarize the mechanisms of action, clinical trials, and FDA approval status of several psychiatric medications that are either newly available or in the FDA approval process. This article highlights medications that demonstrate novel mechanisms of action, examines nonpsychiatric medications that are being used to augment existing psychiatric treatments, and elucidates treatments for illnesses that have not previously received FDA indications.

A Narrative Pharmacological Review of Buprenorphine: A Unique Opioid for the Treatment of Chronic Pain

Buprenorphine is a Schedule III opioid analgesic with unique pharmacodynamic and pharmacokinetic properties that may be preferable to those of Schedule II full μ-opioid receptor agonists. The structure of buprenorphine allows for multimechanistic interactions with opioid receptors μ, δ, κ, and opioid receptor-like 1. Buprenorphine is considered a partial agonist with very high binding affinity for the μ-opioid receptor, an antagonist with high binding affinity for the δ- and κ-opioid receptors, and an agonist with low binding affinity for the opioid receptor-like 1 receptor. Partial agonism at the μ-opioid receptor does not provide partial analgesia, but rather analgesia equivalent to that of full μ-opioid receptor agonists. In addition, unlike full μ-opioid receptor agonists, buprenorphine may have a unique role in mediating analgesic signaling at spinal opioid receptors while having less of an effect on brain receptors, potentially limiting classic opioid-related adverse events such as euphoria, addiction, or respiratory depression. The pharmacokinetic properties of buprenorphine are also advantageous in a clinical setting, where metabolic and excretory pathways allow for use in patients requiring concomitant medications, the elderly, and those with renal or hepatic impairment. The unique pharmacodynamic and pharmacokinetic properties of buprenorphine translate to an effective analgesic with a potentially favorable safety profile compared with that of full μ-opioid receptor agonists for the treatment of chronic pain.

Challenges and opportunities to include patient-centric product design in industrial medicines development to improve therapeutic goals

In the past, drug developers in industry chose approaches mainly focusing on the drug product's efficacy, safety and quality according to the level required by regulatory expectations stipulated in guidelines, pharmacopoeia and other regulatory provisions. By putting more focus on the patient perspective, regulatory authorities are currently raising their requirements regarding successful product submissions. The increasing involvement of patients in the product development process (e.g. conduction of human factor use tests, integration of feedback from patient and patient advisory groups into clinical programmes) requires adaptations to the existing and established industrial drug development processes without compromising fast patient access to innovative therapies. This review provides an expert opinion on the emerging challenges and opportunities to implement a patient-centric approach into new drug development programmes. The aim is to better understand the challenge of finding the right balance between bringing innovative drugs fast to the patients and to develop these in parallel in a patient-centric product form as well as why this is an opportunity and how stakeholder parties (e.g. patients, clinicians, pharmacists, caregivers, regulators) can provide support to achieve desired outcomes.

Retention of patients in opioid substitution treatment: A systematic review

Background

Retention in opioid substitution (OST) treatment is associated with substantial reductions in all cause and overdose mortality. This systematic review aims to identify both protective factors supporting retention in OST, and risk factors for treatment dropout.

Methods

A systematic search was performed using MEDLINE, Embase, PsycInfo, CINAHL and Web of Science (January 2001 to October 2019). Randomised controlled trials (RCTs) and observational cohort studies reporting on retention rates and factors associated with retention in OST were included. Factors associated with treatment retention and dropout were explored according to the Maudsley Addiction Profile. A narrative synthesis is provided.

Results

67 studies were included in this review (4 RCTs and 63 observational cohort studies; N = 294,592), all assessing factors associated with retention in OST or treatment dropout. The median retention rate across observational studies was approximately 57% at 12 months, which fell to 38.4% at three years. Studies included were heterogeneous in nature with respect to treatment setting, type of OST, risk factor assessment, ascertainment of outcome and duration of follow-up. While the presence of such methodological heterogeneity makes it difficult to synthesise results, there is limited evidence to support the influence of a number of factors on retention, including age, substance use, OST drug dose, legal issues, and attitudes to OST.

Conclusions

Younger age, substance use particularly cocaine and heroin use, lower doses of methadone, criminal activity/incarceration, and negative attitudes to MMT appear to be associated with reduced retention in OST. A consensus definition of retention is required to allow for comparability across future studies.

Low intrinsic efficacy for G protein activation can explain the improved side effect profiles of new opioid agonists

Biased agonism at G protein-coupled receptors describes the phenomenon whereby some drugs can activate some downstream signaling activities to the relative exclusion of others. Descriptions of biased agonism focusing on the differential engagement of G proteins versus β-arrestins are commonly limited by the small response windows obtained in pathways that are not amplified or are less effectively coupled to receptor engagement, such as β-arrestin recruitment. At the μ-opioid receptor (MOR), G protein-biased ligands have been proposed to induce less constipation and respiratory depressant side effects than opioids commonly used to treat pain. However, it is unclear whether these improved safety profiles are due to a reduction in β-arrestin-mediated signaling or, alternatively, to their low intrinsic efficacy in all signaling pathways. Here, we systematically evaluated the most recent and promising MOR-biased ligands and assessed their pharmacological profile against existing opioid analgesics in assays not confounded by limited signal windows. We found that oliceridine, PZM21, and SR-17018 had low intrinsic efficacy. We also demonstrated a strong correlation between measures of efficacy for receptor activation, G protein coupling, and β-arrestin recruitment for all tested ligands. By measuring the antinociceptive and respiratory depressant effects of these ligands, we showed that the low intrinsic efficacy of opioid ligands can explain an improved side effect profile. Our results suggest a possible alternative mechanism underlying the improved therapeutic windows described for new opioid ligands, which should be taken into account for future descriptions of ligand action at this important therapeutic target.

Opioid system modulation with buprenorphine/samidorphan combination for major depressive disorder: two randomized controlled studies

The endogenous opioid system is thought to play an important role in the regulation of mood. Buprenorphine/samidorphan (BUP/SAM) combination is an investigational opioid system modulator for adjunctive treatment of major depressive disorder (MDD). To confirm results from early studies, we report the efficacy and safety of BUP/SAM as adjunctive treatment in patients with MDD and an inadequate response to antidepressant therapy (ADT) in FORWARD-4 and FORWARD-5: two phase 3, randomized, double-blind, placebo-controlled studies that utilized the same sequential parallel-comparison design. Efficacy was measured using the Montgomery-Åsberg Depression Rating Scale (MADRS). FORWARD-5 achieved the primary endpoint and demonstrated that adjunctive BUP/SAM 2 mg/2 mg was superior to placebo (average difference change from baseline to week 3 through end of treatment [EOT] in MADRS-6 and -10 versus placebo: -1.5, P = 0.018; -1.9, P = 0.026, respectively). FORWARD-4 did not achieve the primary endpoint (change from baseline in MADRS-10 at week 5 versus placebo: -1.8, P = 0.109), although separate analyses showed significant treatment differences at other timepoints using traditional, regulatory-accepted endpoints such as reduction in MADRS-10 at EOT. The pooled analysis of the two studies demonstrated consistently greater reduction in MADRS-10 scores from baseline for BUP/SAM 2 mg/2 mg versus placebo at multiple timepoints including EOT and average change from baseline to week 3 through EOT (-1.8, P = 0.010; -1.8, P = 0.004, respectively). The overall effect size (Hedges' g) in the pooled analyses for MADRS-10 change from baseline to EOT was 0.22. Overall, BUP/SAM was generally well tolerated, with most adverse events (AEs) being mild or moderate in severity. The most common AEs, occurring in ≥5% of patients in the BUP/SAM 2 mg/2 mg treatment group, which was more frequently than the placebo group, included nausea, constipation, dizziness, vomiting, somnolence, fatigue, and sedation. There was minimal evidence of abuse, and no evidence of dependence or opioid withdrawal by AEs or objective measures. This report describes adjunctive BUP/SAM 2 mg/2 mg combination, a therapy with a novel opioidergic mechanism of action, as a potential new treatment option for patients with MDD who have an inadequate response to currently available ADT.

Decreasing hospital length of stay and enhancing recovery in Total Knee Arthroplasty

BACKGROUND

Patients undergoing Total Knee Arthroplasty (TKA) typically have early postoperative pain and decreased mobility, especially so in the first 24 h. Achieving a pain free knee in the immediate postoperative period and reducing complications using multimodal pain and blood management protocols forms a keystone in early mobilization and functional recovery. Enhanced Recovery after Surgery pathways (ERASp) since their inception, have significantly improved perioperative care and functional outcomes, thereby reducing the average length of stay (ALOS), complications and overall healthcare costs. ERASp modified suitably for TKA have had encouraging results. We have retrospectively analyzed the outcomes of the ERASp for TKA at our tertiary care centre with equal emphasis on pre-hospital preparations, in-hospital care, and post-hospital discharge.

METHODS

All TKA patients operated by the senior author between July 2016 and January 2018 with a minimum one year follow up were included. The outcomes measured were: Visual Analogue Score (VAS) for pain at rest and on movement, milestones, transfusion requirements, postoperative complications, ALOS and functional scores at one year follow-up.

RESULTS

775 patients (392 unilateral TKA {UTKA} and 383 bilateral {BTKA}) met our inclusion criteria. Both groups were comparable demographically. Mean VAS pain scores at rest were 3.15 ± 2.15 on the day of surgery, 2.5 ± 1.86 on the first postoperative day and 2.08 ± 1.81 on the second day, and 6.2 ± 2.38, 5.77 ± 2.34 and 4.71 ± 2.48 on movement respectively in the UTKA group. In the BTKA group, the mean VAS pain scores at rest were 4.39 ± 2.25 on the day of surgery, 3.98 ± 2.36 on the first postoperative day and 3.05 ± 2.12 on the second day and 6.21 ± 2.38, 5.77 ± 2.34 and 4.71 ± 2.48 on movement respectively. 85.49% of UTKA and 77.22% of BTKA patients walked on the day of surgery. Decrease in haemoglobin and transfusion rates were 1.25 ± 0.41 g% and 0.5%, 1.85 ± 0.62 and 3.9% in the UTKA and BTKA groups respectively.The average length of hospital stay (LOS) was 3.98 days. LOS was 3.17 and 4.78 days with 1.55% and 6.05% major complications in the UTKA and BTKA groups respectively.There was a significant improvement in Oxford Knee and WOMAC scores at 3, 6 and 12 months in both groups.

CONCLUSIONS

Pain following TKA is a major deterrent in early mobilization thereby delaying functional recovery and increasing ALOS. We recommend our multimodal interdisciplinary protocol to achieve early mobilization, better pain scores and minimize complications, resulting in overall reduced LOS.

Advances in pain management for older patients with cancer

The population of older patients is growing with a rising prevalence of cancer diagnoses and cancer-related pain syndromes. Older patients are also vulnerable to misleading pain evaluations and under treatment with opioids. Barriers to the effective and safe management of analgesics include pain assessments and the complex management of the best analgesic choice and dose-titration while achieving the fewest side effects. In this review, we will provide an overview of the challenges present in assessment and treatment choices, along with practical tips for routine clinical practice.

The Pharmacokinetics and Local Tolerability of a Novel Sublingual Formulation of Buprenorphine

Aim

The principal study objective was to investigate the pharmacokinetic characteristics and determine the absolute bioavailability and tolerability of a new sublingual (SL) buprenorphine wafer.

Methods

The study was of open label, two-way randomized crossover design in 14 fasted healthy male and female volunteers. Each participant, under naltrexone block, received either a single intravenous dose of 300 mcg of buprenorphine as a constant infusion over five minutes or a sublingual dose of 800 mcg of buprenorphine in two treatment periods separated by a seven-day washout period. Blood sampling for plasma drug assay was taken on 16 occasions throughout a 48-hour period (predose and at 10, 20, 30, and 45 minutes, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 24 and 48 hours postdose). The pharmacokinetic parameters were determined by noncompartmental analyses of the buprenorphine plasma concentration-time profiles. Local tolerability was assessed using modified Likert scales.

Results

The absolute bioavailability of SL buprenorphine was 45.4% (95% confidence interval = 37.8-54.3%). The median times to peak plasma concentration were 10 minutes and 60 minutes after IV and SL administration, respectively. The peak plasma concentration was 2.65 ng/mL and 0.74 ng/mL after IV and SL administration, respectively. The half-lives were 9.1 hours and 11.2 hours after IV and SL administration, respectively. The wafer had very good local tolerability.

Conclusions

This novel sublingual buprenorphine wafer has high bioavailability and reduced Tmax compared with other SL tablet formulations of buprenorphine. The wafer displayed very good local tolerability. The results suggest that this novel buprenorphine wafer may provide enhanced clinical utility in the management of both acute and chronic pain.

Background

Buprenorphine is approved for use in pain management and opioid addiction. Sublingual administration of buprenorphine is a simple and noninvasive route of administration and has been available for many years. Improved sublingual formulations may lead to increased utilization of this useful drug for acute and chronic pain management.

Buprenorphine Maintenance Subjects Are Hyperalgesic and Have No Antinociceptive Response to a Very High Morphine Dose

Objective

Acute pain management in opioid-dependent persons is complicated because of tolerance and opioid-induced hyperalgesia. Very high doses of morphine are ineffective in overcoming opioid-induced hyperalgesia and providing antinociception to methadone-maintained patients in an experimental setting. Whether the same occurs in buprenorphine-maintained subjects is unknown.

Design

Randomized double-blind placebo-controlled. Subjects were tested on two occasions, at least five days apart, once with intravenous morphine and once with intravenous saline. Subjects were tested at about the time of putative trough plasma buprenorphine concentrations.

Setting

Ambulatory.

Subjects

Twelve buprenorphine-maintained subjects: once daily sublingual dose (range = 2-22 mg); no dose change for 1.5-12 months. Ten healthy controls.

Methods

Intravenous morphine bolus and infusions administered over two hours to achieve two separate pseudo-steady-state plasma concentrations one hour apart. Pain tolerance was assessed by application of nociceptive stimuli (cold pressor [seconds] and electrical stimulation [volts]). Ten blood samples were collected for assay of plasma morphine, buprenorphine, and norbuprenorphine concentrations until three hours after the end of the last infusion; pain tolerance and respiration rate were measured to coincide with blood sampling times.

Results

Cold pressor responses (seconds): baseline: control 34 ± 6 vs buprenorphine 17 ± 2 (P = 0.009); morphine infusion-end: control 52 ± 11(P = 0.04), buprenorphine 17 ± 2 (P > 0.5); electrical stimulation responses (volts): baseline: control 65 ± 6 vs buprenorphine 53 ± 5 (P = 0.13); infusion-end: control 74 ± 5 (P = 0.007), buprenorphine 53 ± 5 (P > 0.98). Respiratory rate (breaths per minute): baseline: control 17 vs buprenorphine 14 (P = 0.03); infusion-end: control 15 (P = 0.09), buprenorphine 12 (P < 0.01). Infusion-end plasma morphine concentrations (ng/mL): control 23 ± 1, buprenorphine 136 ± 10.

Conclusions

Buprenorphine subjects, compared with controls, were hyperalgesic (cold pressor test), did not experience antinociception, despite high plasma morphine concentrations, and experienced respiratory depression. Clinical implications are discussed.

Adjuvants in clinical regional anesthesia practice: A comprehensive review

Adjuvants are medications that work synergistically with local anesthetics to help enhance the duration and quality of analgesia in regional techniques. Regional anesthesia has become more prevalent as evidence continues to show efficacy, enhancement of patient care, increased patient satisfaction, and improved patient safety. Practitioners in the perioperative setting need to not only be familiar with regional techniques but also the medications used for them. Some examples of adjuvant medications for regional techniques include dexamethasone, alpha 2 agonists such as clonidine and dexmedetomidine, midazolam, buprenorphine, NMDA antagonists, including ketamine and magnesium, neostigmine, sodium bicarbonate, epinephrine, and non-steroidal anti-inflammatory drugs. The aim of the present investigation, therefore, is to provide a comprehensive review of the most commonly used non-opioid adjuvants in clinical practice today. Regional adjuvants can improve patient safety, increase patient satisfaction, and enhance clinical efficacy. Future studies and best practice techniques can facilitate standardization of regional anesthesia adjuvant dosing when providing nerve blocks in clinical practice.

Opioids in cancer-related pain: current situation and outlook

PURPOSE

Despite progress in treatments, cancer pain remains underestimated, poorly assessed and under-treated. Prescribing strong opioids, because of their specificities, requires precision in management considering their pharmacology but also a clear understanding of recommendations. Some clinicians highlight the risk of addiction, excessive sedation and respiratory depression and their need for information. Our objective in this review is to suggest some clinical guidance for the positioning and daily use of opioids within cancer pain management.

METHODS

Critical reflection based on literature analysis and clinical practice.

RESULTS

Strong opioids may be initiated as soon as pain diagnosis is defined. Factors to consider are pain aetiology, opioid pharmacokinetics and pharmacodynamics, genetic polymorphism, physiology (age, gender, weight and pregnancy), comorbidities (especially renal, hepatic, cardiovascular diseases), chronobiology, environmental factors, medication interference and treatment adherence. Achieving the best-balanced opioid treatment for background pain is complex, mainly due to the variable benefit/risk ratio between individuals and the experience of breakthrough cancer pain. Opioid initiation alongside a dynamic reassessment of pain should be fully integrated into the patient's management to optimise analgesia. The efficacy and safety of a strong opioid treatment need to be re-evaluated and adapted to individuals constantly as it varies over time.

CONCLUSIONS

Cancer pain is multimorphic and permanently changing due to disease evolution, curative treatments and disruptive events (concomitant treatments, pain from associated disease, comorbidities and complications, modifications of the environment). Well-managed opioids are the cornerstone of a complex environment requiring multidisciplinary dynamic assessments integrated into the patient's care pathway.

RETRACTED: Sublingual buprenorphine versus intravenous or intramuscular morphine in acute pain: A systematic review and meta-analysis of randomized control trials

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Authors. The authors have provided a clarification stating that the article does not clearly or fully disclose that it better represents a subset of a previously published manuscript in the British Journal of Anaesthesia (White LD, Hodge A, Vlok R, Hurtado G, Eastern K, Melhuish TM. Efficacy and adverse effects of buprenorphine in acute pain management: systematic review and meta-analysis of randomized controlled trials. (Br J Anaesth. 2018;120:668-678). The papers presented in their meta-analysis are a subset of those in their previous review in the British Journal of Anaesthesia, and do not present additional information beyond their previously published work.

Evaluation of the thermal antinociceptive effects and pharmacokinetics after intramuscular administration of buprenorphine hydrochloride to cockatiels (Nymphicus hollandicus)

OBJECTIVE To evaluate thermal antinociceptive effects and pharmacokinetics of buprenorphine hydrochloride after IM administration to cockatiels (Nymphicus hollandicus). ANIMALS 16 adult (≥ 2 years old) cockatiels (8 males and 8 females). PROCEDURES Buprenorphine hydrochloride (0.3 mg/mL) at each of 3 doses (0.6, 1.2, and 1.8 mg/kg) and saline (0.9% NaCl) solution (control treatment) were administered IM to birds in a randomized within-subject complete crossover study. Foot withdrawal response to a thermal stimulus was determined before (baseline) and 0.5, 1.5, 3, and 6 hours after treatment administration. Agitation-sedation scores were also determined. For the pharmacokinetic analysis, buprenorphine (0.6 mg/kg) was administered IM to 12 of the birds, and blood samples were collected at 9 time points ranging from 5 minutes to 9 hours after drug administration. Samples were analyzed with liquid chromatography-mass spectrometry. Pharmacokinetic parameters were calculated with commercial software. RESULTS Buprenorphine at 0.6, 1.2, and 1.8 mg/kg did not significantly change the thermal foot withdrawal response, compared with the response for the control treatment. No significant change in agitation-sedation scores was detected between all doses of buprenorphine and the control treatment. Plasma buprenorphine concentrations were > 1 ng/mL in all 4 birds evaluated at 9 hours. CONCLUSIONS AND CLINICAL RELEVANCE Buprenorphine at the doses evaluated did not significantly change the thermal nociceptive threshold for cockatiels or cause sedative or agitative effects. Additional studies with other pain assessments and drug doses are needed to evaluate the analgesic and adverse effects of buprenorphine in cockatiels and other avian species.

Effect of Capsaicin and Other Thermo-TRP Agonists on Thermoregulatory Processes in the American Cockroach

Capsaicin is known to activate heat receptor TRPV1 and induce changes in thermoregulatory processes of mammals. However, the mechanism by which capsaicin induces thermoregulatory responses in invertebrates is unknown. Insect thermoreceptors belong to the TRP receptors family, and are known to be activated not only by temperature, but also by other stimuli. In the following study, we evaluated the effects of different ligands that have been shown to activate (allyl isothiocyanate) or inhibit (camphor) heat receptors, as well as, activate (camphor) or inhibit (menthol and thymol) cold receptors in insects. Moreover, we decided to determine the effect of agonist (capsaicin) and antagonist (capsazepine) of mammalian heat receptor on the American cockroach's thermoregulatory processes. We observed that capsaicin induced the decrease of the head temperature of immobilized cockroaches. Moreover, the examined ligands induced preference for colder environments, when insects were allowed to choose the ambient temperature. Camphor exposure resulted in a preference for warm environments, but the changes in body temperature were not observed. The results suggest that capsaicin acts on the heat receptor in cockroaches and that TRP receptors are involved in cockroaches' thermosensation.

Update on opsoclonus-myoclonus syndrome in adults

Opsoclonus-myoclonus syndrome in adults is a rare and heterogeneous disorder with the clinical features of opsoclonus, myoclonus, ataxia, and behavioral and sleep disturbances. The pathophysiology is thought to be immunological on the basis of paraneoplastic or infectious etiologies. Immunomodulatory therapies should be performed although the response may be incomplete. A number of autoantibodies have been identified against a variety of antigens, but no diagnostic immunological marker has yet been identified. This review focuses on underlying mechanisms of opsoclonus-myoclonus syndrome, including findings that have been identified recently, and provides an update on the clinical features and treatments of this condition.

Differences between Transdermal Fentanyl and Buprenorphine in the Elderly Hospice Patients

Introduction

Opioids are the most important drugs in treating pain in palliative care patients. Transdermal formulations are especially useful due to their noninvasive nature and minimal interference in daily life. However, studies have shown a controversial relationship of opioids to survival and a rise in deaths associated with the use of transdermal opioids. Although applying precise doses is paramount, we have no clear recommendations for the exact equianalgesic ratio for buprenorphine patch and no recommendation for the type of transdermal opioid to use in hospice.

Methods

We analyzed the differences between the transdermal fentanyl and buprenorphine group by analyzing patient characteristics and evaluating the differences in survival in hospice patients over the age of 65, from 2013 to 2017.

Results

A total of 292 patients (75.8%) used fentanyl patch and 93 (24.1%) were on buprenorphine patch. Patients had virtually the same characteristics in both groups. However, when using a 1:100 buprenorphine equianalgesic ratio, there were significant differences in initial and final doses, and it seems that a 1:80 conversion rate is more accurate for elderly hospice patients. Finally, there was no difference in survival between the two groups using transdermal opioids, with or without adjuvant analgesics.

Discussion

There were no differences in survival between the group using transdermal fentanyl and the group using buprenorphine in the elderly hospice population. Although adjuvant NSAIDs could be useful in the treatment of pain in terminal cancer, they do not affect survival or reduce the opioid doses, while a 1:80 equianalgesic ratio of buprenorphine might be the most appropriate in this population.

Efficacy and Safety of Analgesic Treatment for Depression in People with Advanced Dementia: Randomised, Multicentre, Double-Blind, Placebo-Controlled Trial (DEP.PAIN.DEM)

Background

Chronic pain and depression often co-occur, and pain may exacerbate depression in people with dementia.

Objective

The objective of this study was to assess the efficacy and safety of analgesic treatment for depression in nursing home patients with advanced dementia and clinically significant depressive symptoms.

Methods

We conducted a multicentre, parallel-group, double-blind, placebo-controlled trial in 47 nursing homes, including 162 nursing home patients aged ≥ 60 years with dementia (Mini-Mental State Examination ≤ 20) and depression (Cornell Scale for Depression in Dementia ≥ 8). Patients were randomised to receive active analgesic treatment (paracetamol or buprenorphine transdermal system) or identical placebo for 13 weeks. The main outcome measure was the change in depression (Cornell Scale for Depression in Dementia) from baseline to 13 weeks, assessed using linear mixed models with fixed effects for time, intervention and their interaction in the models. Secondary outcomes were to assess whether any change in depression was secondary to change in pain (Mobilisation-Observation-Behaviour-Intensity-Dementia-2 Pain Scale) and adverse events.

Results

The mean depression change was − 0.66 (95% confidence interval − 2.27 to 0.94) in the active group (n = 80) and − 3.30 (− 4.68 to −1.92) in the placebo group (n = 82). The estimated treatment effect was 2.64 (0.55–4.72, p = 0.013), indicating that analgesic treatment had no effect on depressive symptoms from baseline to 13 weeks while placebo appeared to ameliorate depressive symptoms. There was no significant reduction in pain in the active treatment group (paracetamol and buprenorphine combined) vs. placebo; however, a subgroup analysis demonstrated a significant reduction in pain for paracetamol vs. placebo [by − 1.11 (− 2.16 to − 0.06, p = 0.037)] from week 6 to 13 without a change in depression. Buprenorphine did not have significant effects on depression [3.04 (− 0.11 to 6.19), p = 0.059] or pain [0.47 (− 0.77 to 1.71), p = 0.456] from 0 to 13 weeks. Thirty-five patients were withdrawn from the study because of adverse reactions, deterioration or death: 25 (31.3%) during active treatment [23 (52.3%) who received buprenorphine], and ten (12.2%) in the placebo group. The most frequently occurring adverse events were psychiatric (17 adverse reactions) and neurological (14 adverse reactions).

Conclusion

Analgesic treatment did not reduce depression while placebo appeared to improve depressive symptoms significantly by comparison, possibly owing to the adverse effects of active buprenorphine. The risk of adverse events warrants caution when prescribing buprenorphine for people with advanced dementia.

Trial registration

ClinicalTrials.gov NCT02267057 (registered 7 July, 2014) and Norwegian Medicines Agency EudraCT 2013-002226-23.

Electronic supplementary material

The online version of this article (10.1007/s40266-018-0546-2) contains supplementary material, which is available to authorized users.

Treating Chronic Pain: An Overview of Clinical Studies Centered on the Buprenorphine Option

The buprenorphine receptor binding profile is unique in that it binds to all three major opioid receptors (mu, kappa, delta), and also binds to the orphan-like receptor, the receptor for orphanin FQ/nociceptin, with lower affinity. Within the mu receptor group, buprenorphine analgesia in rodents is dependent on the recently discovered arylepoxamide receptor target in brain, which involves a truncated 6-transmembrane mu receptor gene protein, distinguishing itself from morphine and most other mu opioids. Although originally designed as an analgesic, buprenorphine has mainly been used for opioid maintenance therapy and only now is increasingly recognized as an effective analgesic with an improved therapeutic index relative to certain potent opioids. Albeit a second-, third-, or fourth-line analgesic, buprenorphine is a reasonable choice in certain clinical situations. Transdermal patches and buccal film formulations are now commercially available as analgesics. This review discusses buprenorphine pharmacodynamics and pharmacokinetics, use in certain populations, and provides a synopsis of systematic reviews and randomized analgesic trials. We briefly discuss postoperative management in patients receiving buprenorphine maintenance therapy, opioid equivalence to buprenorphine, rotations to buprenorphine from other opioids, and clinical relevance of buprenorphine-related QTc interval changes.